In the present invention, there are disclosed submersible strains Quambalaria sp. CCM 8372 and CCM 8373, process for their preparation by fermentation, separation and purification of extra- and intracellular naphthoquinone dyes produced by filamentous fungi of the Quambalaria sp strain, naphthoquinone dye FSK1 (3-(5-ethyl-tetrahydrofuran-2-ylidene)-5,7,8-trihydroxy-2-oxo-1,4-naphthoquinone), a mixture of naphthoquinone dyes containing FSK1, FSK2 (3-(hexyl-1-one)-2,5,7,8-tetrahydroxy-1,4- naphthoquinone) and mompain, the use of the or the compound FSK2.